This invention relates generally to a solenoid valve assembly for controlling a valve to an opened and closed condition in accordance with the supply of electric power to a solenoid and more particularly to a solenoid valve assembly having a valve member movably supported on an elastic member such as a diaphragm.
A prior art solenoid valve assembly is disclosed in Japanese Published Patent Application No. 62(1987)-113977 published on May 25, 1987. The basic structure of the solenoid valve assembly in the application is shown in FIG. 7A. A valve member 1 for engaging and disengaging with a stationary valve seat (not shown) is inserted in a central portion of a diaphragm 2 so as to move in the direction of thickness of diaphragm 2. The valve member 1 is fixed to a moving core 3 made of a magnetic material so as to move the valve member 1 electro-magnetically. In the embodiment of FIG. 7A, the stationary valve seat is arranged on the left side of valve member 1 and the valve member 1 is engaged with the valve seat under the non-excited condition of a solenoid (not shown). Furthermore, a stationary core (not shown) made of a magnetic material is located on the right side of moving core 3 and the moving core 3 is moved in the right direction by an attracting force generated at the stationary core under the excited condition of the solenoid whereby the valve member 1 is disengaged from the valve seat.
When the solenoid is excited so as to move the valve member 1 to the opened condition, the moving core 3 moves in the direction of arrow A as shown in FIG. 7B whereby the valve member 1 is subjected to a force indicated by the arrow B which is the restoring force of diaphragm 2. Accordingly, the moving core 3 and valve member 1 are subjected to opposed forces. Consequently, in the conventional solenoid assembly, an adhesive between the moving core 3 and valve member 1 may fail, causing a separation of the core 3 and the valve 1. More specifically, in a solenoid valve assembly controlling an amount of fluid passing through a valve with duty control, the force separating the valve member 1 from moving core 3 is repeated in a short period whereby the possibility of a malfunction is very high.
Furthermore, in the prior art solenoid valve assembly disclosed in the above Japanese Published Patent Application No. 62(1987)-113977, the restoring force of diaphragm 2 increased rapidly when the moving core 3 approaches the stationary core so as to avoid the engagement of moving core 3 with the stationary core. Therefore the force separating the valve member 1 from moving core 3 is strong, whereby the possibility of a malfunction is very high in comparison with a standard solenoid valve assembly.
If the moving core is supported on the diaphragm, the possibility of separation of the moving core from the valve member will disappear. However, in such a case, the diaphragm is easy to break due to the fact that the moving core is a rigid body whereby the malfunction cannot be avoided.